It depends on your goals and traffic pattern. If this machine is to serve lots of multiple different clients then the issue you're running into during testing would probably go away. The throughput is limited when the traffic is all going to one place, when it goes to multiple places then each one could potentially use a different link.

There is a big discussion in the section "12. Configuring Bonding for Maximum Throughput" in /usr/share/doc/kernel-doc-3.10.0/Documentation/networking/bonding.txt which is part of the kernel-doc package. You can also alter how the traffic is distributed by changing the hashing mechanism.

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